The present invention relates to alternators, and more particularly to an alternator designed such that the stator carries both field and armature windings.
As with rotating electric motors, alternators include two major mechanical parts; the stationary part, referred to as the stator, and a part which rotates on bearings within the stator, called the rotor. In conventional alternator design, both the rotor and the stator carry windings. The rotor is mechanically driven by an external machine, for example an internal combustion engine, and one of the windings (the field winding) is energized. This induces a voltage in the other winding (the armature winding), which can be rectified and used as the source of electric potential for charging a battery, for example.
Since, except in permanent magnet electrodynamic machines, the rotor will normally carry a winding, some means must be provided for coupling electrical power into or out of this winding. To accomplish this, the rotor normally carries slip rings which are contacted by stationary brushes. These brushes and slip rings are one of the major trouble points in an alternator, since they can be fouled by grease, dirt, etc. and because they are prone to wear. It would clearly be desirable to devise an alternator which did not require the inclusion of windings on the rotor, thereby avoiding the need for the brushes and their associated slip rings, or any other means for coupling electrical power into or out of the rotor.
Alternators having windingless rotors have been devised in the past, and are disclosed in the following U.S. Pat. Nos. 3,157,810; 3,173,076; 3,512,026; and 4,075,521.